Gear-cutting tool



Sept. 19, 1944. 1.. o. CARLSEN GEAR CUTTING TOOL Filed Aug. 1, 1941 2Sheets-Sheet '1 inventor LEON/9RD 0. CHRLSE/V Sept. 19, 1944.- L. o.CARLSEN 2,358,439

- I "GEAR CUTTING- T60L Filed Aug. 1, 1941 2 Shets-Sheet 2 6 ZSnventor[ION/9RD 0. chm SEN attorney Patented Sept. 19, 1944 GEAR-CUTTING TOOLLeonard 0. Carlson, Rochester, N. 'Y., assignorto Gleason Works,Rochester, N. Y., a corporation of New York Application August 1, 1941,Serial No. 405,064

12 Claims.

The present invention relates to a method of and to a toolfor cuttinggears and particularly to a method of and tool for cutting fine-pitchstraight bevel gears. The present application is confined to the newtool. The novel method of the present invention is covered in adivisional application, Serial No. 451,536, filed July 20, 1942.

Considerable metal has to be removed from the interdental spaces ofgears of coarse pitch in order to produce the final finished tooth form.It is the practice, therefore, to rough-cut such gears to approximateshape before taking the finishing cut. In very fine pitch jobs, however,the amount of metal, that has to be removed. in order to form the toothspaces, is quite small. For reasons of economy,'then,-such gears may becut from the solid in one operation without any preliminary roughingout. With the tools and cutting methods heretofore employed, however, ithas been difficult ina single cut or so-called completing operation toobtain an entirely smooth tooth surface finish, for the cutting edgeswhich rough out the tooth space have also to finish the tooth sides.Furthermore, in the completing method, the tooth spacing sometimes doesnot have the required accuracy because the cutting thrusts are differenton the two tools. Hence, where the requirements of finish and accuracyare high, it has been the practice heretofore to take separate roughingand finishing cuts on' fine pitch jobs as well as on coarse pitch jobs.

One object of the invention is to provide a combined roughing andfinishing tool for cutting gears in a reciprocatory planing operationwhich has separate roughing and finish cutting parts that are arrangedto operate successively on a gear blank as the tool is reciprocatedacross the face of the blank.

Another object of the invention is to provide a combined roughing andfinishing planing tool in which both the roughing and finishing partsmay be sharpened with front rake .so as to obtain very keen cuttingaction.

Still another object of the invention is to provide a combined roughingand finishing planing tool which is so constructed that the finishingpart will out on one side only of the tooth space so that when thefinishing cut is being taken, there will be no other cutting thrusts onthe tool to disturb the accuracy of thefinishing operation.

Other objects of the invention will be apparent hereinafter from thespecification and from the recital of the appended claims.

For completing gears by the method of the present invention, a pair of.reciprocatory planing tools are employed. -Each tool has aroughing partand a finishing part, and the roughing part is arranged in advance ofthe finishing part in the direction of reciprocation of the tool. In thepreferred construction, the roughing part is sharpened to cut on oneside of a tooth space and the finishing part of a tool is sharpened tocut on the opposite side of that tooth space. In the preferredconstruction, the finishing part is made to a greater actual height thanthe roughing part but its actual height is so selected with reference tothe height of the roughing part that when the tool is tipped to the topclearance angle required for cutting, that is, when the tool isin actualcuttingposition, the finishing part will notproject into the tooth spaceas far as the roughing part of the tool. Thus the roughing .part of thetool-will relievethe tip of the finishing part of the tool of all or ofpractically all cutting, and .the finishing part will cut substantiallyon. the side of a tooth space only.

Asalready stated, the tools are preferably sharpened so that theroughing and finishing parts of a tool will operate on .opposite sidesof a tooth space of the blank. Preferably the two tools are so sharpenedand arranged that their finishing edges will operate, respectively, onthe adjacent opposite sides .of two adjacent tooth spaces of a blankwhile the roughing edges operate on theremotely spaced opposite sides ofthose same two tooth spaces. The finishing edges of the two tools, inother words, are preferably arranged to cut on opposite sides of thesame,

tooth. On each cutting stroke of a tool, the roughing part .of the toolengages the blank first and takes a cut in the bottom and on one side ofa tooth slot. Then the finishing part takes its out on the opposite sideof the tooth slot. The two tools are stroked back. and forth, cuttingever further into the blank with feed or roll until the tooth space isfinished. Then the tools are withdrawn from engagement, with the blank,

and the blank is indexed. During the cutting of the first two toothspaces of the blank, two slots are roughed out and the adjacent oppositesides of those slots, which bound a tooth, are finished. Thereafter,when the blank is indexed from tooth to tooth, one tooth slot is roughedand one side thereof finish-cut by one tool While the other tooltaper-cuts and finishes the opposite side of a tooth slot which haspreviously been operated on by the first tool. As already stated, whenthe blank has been indexed through one revolution, th gear is completed.

The present invention may be practiced on any standard straight bevelgear cutting machine of the two tool type by simply substituting for theconventional type of planing tools, tools made according to the presentinvention.

In the drawings: 7

Fig. 1 is a front elevation of the tool end of a standard type two-toolstraight bevel gear generator, showing a pair of planing tools madeaccording to the present invention mounted thereon for practicing thisinvention;

Fig. 2 is a plan view of a planing tool made according to the presentinvention;

Fig. 3 is a fragmentary end elevational view of this tool on an enlargedscale;

Fig. 4 is a diagrammatic view on an enlarged scale, showing a pair ofthe improved type of planing tools in engagement with a gear blank andillustrating the process of the present invention; and

Fig. 5 is a fragmentary plan view and Fig. 6 is a fragmentaryelevational view with the tool shownin section on the line 6--6 of Fig.5, further illustrating the process of the present invention.

As, already stated, the process of the present invention may bepracticed on any conventional type of two-tool straight bevel geargenerator.

In Fig. 1 I have shown the tool end of a machine on adjustable toolarmsI4 and I5, respectively.

which connect the blocks with the tool slides l2 and. I3, respectively.The tool arms I4 and I5 are adjustable angularly in accordance with theangle of longitudinal convergence of opposite sides of the teeth of thegear to be cut. Each toolcuts on the stroke of its slide in onedirection and isout of cutting position on the return stroke of itsslide, the pivotal tool boxes H1 and II being swung to and from cuttingposition at opposite ends of the stroke of their respective slides bythe clapping mechanisms of the machine. The tool slides travelsimultaneously in opposite directions under actuation of their crankdriven reciprocating mechanism. Hence one tool will be cutting on thecutting stroke of its slide While the other tool is in withdrawnposition on present invention is shown in Figs. 2 and 3. The

body portion of this tool is denoted at 25. It is provided with holes 26through which screws 21 or 28 may be passed to secure the tool to one ofthe tool boxes II], or II of the machine.

The cutting portion of the tool consists of three parts designated as30, 3| and 32, respectively. 30 and 32 are rough-cutting parts, and 3|is a finish-cutting part. The two roughing parts are provided simply asa matter of economy so that a given tool may be used at will on eitherthe upper or lower tool slide of a given gearcutting machine, as willappear hereinafter.

Only one roughing part 30 or 32 is operative in any given position ofthe tool.

The roughing parts 30 and 32 are similar. Each is of truncated wedgeshape and has plane opposite side surfaces 34 and 35 and a plane tipsurface 36. The front face 38 of the part 30 is sharpened with a hookand side rake to provide a side-cutting edge at the juncture of thefront face 39 with the side 35- and a tip-cutting edge at the junctureof the tip face 36 with the front face 38. Similarly, the rear face 40of the part 32 is sharpened with a hook and side rake to provide sideand tip cutting edges at the junctures of the rear face 40 with one sideand the tip of this part 32. The side-:cutting edge 4| for therear part32 lies at the same side of the blade as the side cutting edge 39 of thefront roughing part 3|].

The finishing part is separated from the roughing parts 30 and. 32 bygrooves 41 and. 48. It is also of truncated V-shape, having planeopposite sides 44 and 45 and a plane'top surface 45. It has its two endfaces 49 and 50 sharpened with hooks and side rakes to provideside-cutting edges 5| and 52, respectively.

The front and rear cutting faces 39 and 4|] of the roughing parts 30 and32, respectively, and the front and rear faces 49 and 50 of thefinishing part 3| permit of using the same tool on either the upper orlower tool slides ID or II by simply reversing the tool end for end.When the tool is positioned on the lower tool slide l3, the side-cuttingedge 39 of the roughing part 30 and the side cutting edge 5| of thefinishing part 3| are effective. When the tool is positioned on theupper slide I2, the side-cutting edge 4| of the roughing part 32 and theside cutting edge 52 of the finishing part 3| are effective.

The tool is so made'that side-cutting edges 39 and 4| of its roughingparts are offset laterally beyond the corresponding side face 45 of thefinish-cutting part 3|. Likewise, the tool is so constructed that theside-cutting edges 5| and 52 of the finishing part 3| are offsetlaterally to the opposite side beyond the corresponding sidefaces 34 ofthe roughing parts. This construction is illustrated clearly in Fig. 3where 1' denotes the width of the roughing part 3|] at its tip and fdenotes the width of the finishing part 3| at its tip.

The finishing part 3| of a tool projects in height a distance (1 beyondthe tops 36 of the roughing parts 30 and 32, but when the tool isarranged in actual cutting (position, its tip is inclined to the rootplane of the work at an angle equal to the top clearance angle requiredfor good cutting action. Thus, as shownin Fig. 5, the tool T is inclinedto the root surface 55 of the gear G, that is to be cut, at a topclearance angle 0. This angle is ordinarily 12. To relieve the tip ofthe finishing part of cutting, the distance d (Fig. 3) which thefinishing part projects beyond the roughing part, is ordinarily madesuch that when the tool is in cutting position, the finishing part willnot cut as deeply as the roughing part of the tool. This is shown inFig. 5. As will be seen, while the tip of the roughing part 30, in fulldepth position, travels in the root plan 55 of the tooth space, the tipof the finishing part 3| travels on a line 56 which is parallel to theroot plane but above the root plane. The distance d of projection of thefinishing part 3| beyond the roughing part 30 or 32 i equal to thedistance s (Fig. 2) from the front face of the roughing part to thefront face acreage!) of the finishing apart times the tangent of the topclearance angle .c less ordinarily 02" i(two thousandths of an inch).The 5002" will usually provide suficient clearance so that the vtipofthe finishing part of the .tool will not rub on the bot'tomof th toothspace.

In the cutting :operation, the two tools T and T are reciprocatedbackand 'forth across the face of the gear blank in paths convergingtoward the cone :apex 59 of the gear blank, during roll or feed of thetools into the work. In the preferred construction, the effectivepoint-width of each tool, which is the distance between thefinish-cutting edge 51 or 52 and the rough-cutting edge :39 or 41measuredin-the plane of the tip of either the finishing .or the roughingpart, is "less than the width of the two spaces of the gear tobe cut atthe small .ends of said tooth spaces. As wiIl be-seen in Figs. 4'and 6,during cutting of the first two tooth'space's of a gear blank, then, theside edge 39 and the tip edge 36 er the roughing part 30 of the lowertool Tand the side-cutting edge 51 of the finishing part 3| of this toolwill cut a tooth slot 60 in the blank which has paralll sides, and whichis of less width than the width of a finishedftooth space. Further, oneside 6! of this tooth space will be finished by the finish-cutting edge51. Sunultaneous'ly, the side edge 39 and tip edge 36 of the roughingpart 32 of the upper tool T and the finished-cutting edge 52 of this'tool T' will cut a tooth slot 62 which has parallel sides and'which isalso o'f'less width than a finished tooth space. This tooth slot-62 isinclined to the'slot =60 *because the paths of travel of the two toolsare inclined-to one another. Thus two tooth slots '60 and 62 will beroughed out and'the two sides 61 and63 thereof, which bound the tooth 65of the gear, will be finished.

After the tooth slots 60 and 62 have been out to full depth, the toolsare withdrawn from the blank and the blank indexed. If the indexing isin the direction'of the arrow 66 (Fig. 4), then when the tools are 'fedback into engagement with the blank, the tool T will operate in thetooth slot'62 while the tool T will operate in the tooth slot bounded bythe dotted'lines 6'! and'-'68. Since the tool T travels on a path whichis inclined longitudinally to the path of travel of the tool T, thefinish cutting edge 5| of the tool Twill remove the 'stockbetween theroughed 'side surface =69 of the tooth slot 62 and the finished side T0thereof, producing the final finished tooth surface and completing thefinishing of the tooth slot. Simultaneously the tool T' will rough outthe tooth slot H bounded by the sides -61 and B8 and will finish theside 68 of this tooth slot. Thus the operation will proceed. During eachcutting cycle, the tool T' will rough out a slot and finish one sidethereof,

while the tool T will finish the opposite side of a tooth slot which haspreviously been operated upon by the tool Tf. During the last cuttingcycle, the'finish side-cutting edge 52 of the tool T will finish thetoothslot 60 of the blank, re-

moving the stock between the roughed tooth surface 12 and the finishedtooth side 13, producing the finished tooth side. Simultaneously thetool T will be removing the 'stock'between the roughed side 16 and thefinished side surface 11 of the tooth slot 15, which will previouslyhave been roughed out and partly finished by the tool T. Thus, when theblank has been indexed through a revolution, the gear will have beencompleted.

While the invention has been describedin connection with afinish-cutting operation, it will be understood that it may :also :beused FfOI' roughcutting, particularly on coarse pitch jobs. In thislease, :the different :sections of the tool will allibe roughing parts.Arroughing-tool so made will .cut more smoothly and more rapidly. thanconventional planing tools because its cutting edges are :sharpers'inceopposite :side rake is provided'on the successiveparts-of the tool. Inthis case, the heightof the central .section 3| of the tool may be :made:such that it will be of the same effective cutting height as *that ofthe front operating section .of :the vtool, or the heights of the twoparts may be unequal as in the illustrated embodiment of the invention.

.Further, while the tool has :been described as having three sections soas to be reversible, it will be understood that it may, if desired, bemade :simply-with-two sections and be used for its full efiective' lif'e:on either the upper or-lower tool slide only.

Still "further while the invention has been illustrated in "connectionwith tools having straight side-cutting edges whose cutting partsarfe'rof prismatic form, having .plane side and tip surfaces, it will beunderstood that the sides and cutting'edges of the tool may be made toany shape" usual or desirable in a gear planing tool. Moreover, whilethe cutting parts of the tool shown have unrelieved sides and tips, itwill be understood that the tool may have its sides and tips'irelievedif (desired. If the tips of the cutting parts-are ire'lieved, that is,are inclined to the basex'of thetool at'the desired top cutting clearance angle, then of course, the tool need not be tiltedand in thisevent, of course, if it is desired to have the tipeutting :edge of theroughing part do .the tipacutting, the .actual height of thefiniSh-cutting-part will .be'slig'htly less (.002" or so) than theactual height of the roughing part.

For cutting certain materials, such as phosphoribronze, the roughing orfinishing part or both "may be sharpened without side rake to getascraping rather than a shaving action.

Further, while the tools shown have the rough ing;and finishingpartsintegral, it will be understoodrthat theseparts may be made separatefrom one another and that each tool may comprise separateroughing andfinishing parts that are secured in 1a singletool holder.

Other modifications anduses of the invention will occur to thosesk-illedin the 'art. The present application is intended to cover anyadaptations, uses, or embodiments of the invention following, ingeneral, the principles of the inventime and including-such departuresfrom the present disclosure as come within known or custernary practicein the gear art and as may be applied to the essential featureshereinbefore set forth and as fall within the scope of the invention orthe limits o'f'the appended claims.

Having thus described my invention, what I claim is:

'1. A reciprocatory planing tool for gear cutting having two cuttingparts which are arranged one behind the other in the direction ofcutting movement of the tool, each of said parts being of generallyprismatic shape and having unrelieved side and tip surfaces, 'wherebythe tool must :be tilted in use so that its tip surface is inclinedtoythe plane of cut to provide cutting clearance, the rear cutting partbeing of greater actual 'height 'than the front cutting part, the pointof juncture of-'one side of the frontcutting part with "the tip :of thatcutting part being more ofiset and the point of juncture of the oppositeside of the front cutting part with the tip of that cutting part beingless offset from a median line of the tool than the points of junctureof opposite sides, respectively, of, the rear'cutting part with the tipof the latter cutting part.

2. A reciprocatory planing tool for gear cutting having two cuttingparts which are arranged one behind the other in the direction ofcutting movement of the tool, the rear cutting part being of greateractual height than the front cutting part, both parts being of generallyprismatic shape and having sides and tips unrelieved, whereby the toolmust be tilted in use so that its tip surface is inclined to the planeof cut to provide cutting clearance, the rear part projecting in heightbeyond the front part a distance less than the distance between thefront faces ofthe two parts times the tangent of the angle to which thetool is tilted in use for top cutting clearance.

3. A reciprocatory planing tool for gear cutting having two cuttingparts Which are arranged one behind the other in the direction ofcutting movement of the tool, both of said parts being of generallyprismatic shape and having sides and tips unrelieved, whereby the toolmust be tilted in use so that its tip surface is inclined to the planeof cut to provide cutting clearance, the rear cutting part being ofgreater actual height than the front cutting part but of less cuttingheight when the tool is tipped to the clearance angle, the front partbeing sharpened to have a side-cutting edge at one side and a tipcutting edge, and the rear part being sharpened to have a side-cuttingedge at the side opposite to the side-cutting edge of'the front part,the side cutting edge of each cutting part being more offset from amedian line of the tool than the corresponding non-cutting side of theother cutting part.

4. A reciprocatory planing tool for gear-cutting having a front, anintermediate,and a rear cutting part arranged one behindthe other in thedirection of cutting movement of the tool, the front cutting part beingsharpened on its'front face, the rear cuttingpart being sharpened on itsrear face, and the intermediate cutting'part being sharpened on both itsfront and rear faces so that the tool may be reversed end for end.

5. A reciprocatory planing tool for gea cutting having a front, anintermediate, and a rear cutting part arranged one behind the other inthe direction of cuttin movement of the tool, the front and rear cuttingparts being of the same height but being of less actual height than theintermediate part, all of said parts being unrelieved, the front cuttingpart being sharpened on its front face, the rear cutting part beingsharpened on its rear face, and the intermediate cuttingpart beingsharpened on both its front and rear faces so that the tool may bereversed end for end.

6, A reciprocatory planing tool for gear cutting having a front, anintermediate, and a rear cutting part arranged one behind the-other inthe direction of cutting movement of the tool, the front cutting partbeing sharpened on its front face to have a side-cutting edge lying atone side of the tool, the rear cutting part being sharpened on its rearface to have a side-cutting edge lying at the same side of the tool asthe sidecutting edge of the front part, and the intermediate part havingone side face offset laterally with reference to the corresponding sideface of the front and rear parts and being sharpened on both its frontand rear faces to have front and rear side-cutting edges lying at thejunctures of its front and rear faces with its offset sideface. 7. Areciprocatory planing tool for gear cutting, having two cutting partsarranged one behind the other in the direction of cutting movement Ofthe tool, each cutting-part being of generally prismatic shape andhaving a plane tip surface and opposite sid surfaces which are alsoplane and which converge toward the tip surface, said surfaces beingunrelieved whereby the tool must be tilted in use so that its tipsurface is inclined to the plane of cut to provide cutting clearance,said cutting parts being sharpened to have side cuttin edges at oppositesides of the tool, respectively, the rear cutting part having greateractual height than the front cutting part but having a lesser effectivecutting height,'and the cuttingedge of each part being offset outwardly,respectively, with reference to the corresponding non-cutting side ofthe other part. 7

8. A reciprocato-ryrplaning tool for gear cutting having two cuttingparts arranged one behind the other in the direction of cutting movementof the tool, each cutting part being of generally prismatic shape andhaving opposite side surfaces which converge toward the tip surface ofsaid part, said cutting parts being sharpened to have side cutting edgesat opposite sides of the tool, respectively, the side cutting edge ofeach part being ofiset outwardly beyond the non-cutting side of theother part, the side and tip surfaces of each part being unrelieved,whereby the tool must be tilted in use so that its tip surface isinclined to the plane of cut to provide cutting clearance, the rearcutting part projecting in height beyond the front cutting part adistance slightly less than the longitudinal distance between the sidecutting edges of the two parts times the tangent of the angle t whichthe tool is tilted for top cutting clearance in use.

9. A reciprocatory planing tool for gear cutting having a front, anintermediate, and a rear cutting part arranged one behind the other inthe direction of cutting movement of the tool, the front cutting partbeing sharpened on its front face, the rear cutting part being sharpenedon its rear face, the intermediate cutting part having one side facewhich is offset laterally with reference to the corresponding side ofthe front and rear cutting parts, and said intermediate cutting parthaving both its front and rear faces sharpened to provide side cuttingedges at the junctures of its front and rear faces with its offset sideface. 7

10. A reciprocatory planing tool for gear cutting having a front, anintermediate, and a rear cutting part arranged one behind the other inthe direction of cutting movement of the tool, each of said parts beingofgenerally prismatic shape and havingits sides and tip unrelieved, theintermediate cutting part being of greater actual height than either thefront or rear parts, the front cutting part being sharpened on its frontface, the rear cutting part being sharpened on its rear face, theintermediate cutting part having one side face which is offset laterallywith reference to the corresponding sid of the front and rear cuttingparts, and said intermediate cutting part having both its front and rearfaces sharpened to provide side cutting edges at the jih'ictures of saidfront and rear faces with its offset side face.

'11. A reciprocatory gear-cutting tool having two cutting parts whichare arranged, respectively, one behind the other in the direction ofcutting movement of the tool, each of the cutting parts havingopposite'sides which converge to the tip of the cutting part and each ofsaid parts having its sides and tip unrelieved whereby the tool must betilted in use so that the tip surfaces of said parts are inclined to thplane of cut of the tool to provide cutting clearance, the points ofjuncture of opposite sides of the front cutting part with the tip ofthat cutting part being more and less offset, respectively, from amedian line of the tool than the points of juncture of the oppositesides, respectively, of the rear cutting part with the tip of the rearcutting part, and the rear cutting part being of greater height.

12. A reciprocatory gear-cutting tool having two cutting parts which arearranged, respectively, one behind the other in the direction of cuttingmovement of the tool, each of the cutting parts having opposite sideswhich converge to its tip, both of said parts having sides and tipsunrelieved whereby the tool must be tilted in use so that its tipsurfaces are inclined to the plane of cut of the tool to providecuttingclearance, the front faces of the two cutting parts beingsharpened in opposite directions to provide side cutting edges whichlie, respectively, at opposite sides of the tool, the point of junctureof the side cutting edge of each cutting part with the tip of thatcutting part being more ofiset from a median line of the tool than thecorresponding non-cutting side of the other cutting part, the rearcutting part being of greater height than the front cutting part.

LEONARD O. CARLSEN.

